Apparatus for monitoring a thread or the like

ABSTRACT

An apparatus for monitoring the travel and tension of a thread or the like preferably at a textile machine, comprising a guide element which is held by a counter force against a tension force normally exerted by the thread in a position in which the thread is in contact with the guide element, but upon the presence of an impermissibly high tension force releases the thread. The guide element is equipped with a mechanical-electrical transducer possessing a contact body, the transducer, upon release of the thread from the contact body or upon standstill of the thread, generating an electrical signal serving to trigger a control operation or an indicating operation.

United States Patent Domig June 24, 1975 [54] APPARATUS FOR MONITORING A2,956,392 10/1960 0111115111 ZOO/61.18

THREAD OR THE LIKE 3,676,769

Inventor: Ren Domig, Kusnacht, Switzerland Aktiengesellschaft GebruderLoepfe, Zurich, Switzerland Filed: Mar. 18, 1974 Appl. No.2 452,993

Assignee:

Foreign Application Priority Data Mar. 30, 1973 Sweden 734594 ReferencesCited UNITED STATES PATENTS 11/1920 Wachsman 66/161 7/1972 Loepfe139/378 Primary Examiner-Mervin Stein Assistant ExaminerSteven HawkinsAttorney, Agent, or Firm-Werner W. Kleeman 5 7] ABSTRACT An apparatusfor monitoring the travel and tension of a thread or the like preferablyat a textile machine, comprising a guide element which is held by acounter force against a tension force normally exerted by the thread ina position in which the thread is in contact with the guide element, butupon the presence of an impermissibly high tension force releases thethread. The guide element is equipped with a mechanicalelectricaltransducer possessing a contact body, the transducer, upon release ofthe thread from the contact body or upon standstill of the thread,generating an electrical signal serving to trigger a control operationor an indicating operation.

9 Claims, 6 Drawing Figures APPARATUS FOR MONITORING A THREAD OR THELIKE BACKGROUND OF THE INVENTION The present invention relates to a newand improved construction of apparatusfor monitoring the travel andtension of a thread or the like, preferably at a textile machine, of thetype incorporating a guide element which is retained by a counter force,against the action of a tension force normally exerted by the thread, ina position in which the thread is in contact with the guide element, butin the presence of an impermissibly high tension force releases thethread.

In the context of this disclosure, the term thread is intended to beunderstood as being employed in its broadest sense as covering varioustypes of filamentary material, such as threads, yarns or the like. i

There are already known to the art such abovementioned general types ofmonitoring devices which are employed at circular knitting machines andwhich are equipped with two fork-like feeler levers which in terengagewith one another and which are known in the art under the designationplucking or pick monitors.

The thread to be monitored bears against the fork tongs of onespring-loaded feeler lever and rocks such downwardly against the forceof the spring when the thread tension becomes impermissibly great, sothat the thread is then released from such feeler lever. The secondfeeler lever which is loaded by a counter weight bears with its tongsfrom below against the thread and rocks upwardly as soon as threadrupture occurs or the thread tension falls below a predeterminedboundary value. In the aforementioned cases both levers actuate anelectrical contact by means of which there is triggered standstill orshutdown of the machine.

With the heretofore known plucking monitors there are thus provided forthe purpose of monitoring the thread tension, with respect to an upperand lower boundary value, two separate mechanical-electrical operatingfeeler elements which, of necessity, exhibit a relatively largemechanical inertia and thus respond rather slowly. Additionally, theelectrical contacts which are present are subject to contamination andcorrosion, thereby impairing the operational reliability of themonitoring device. Also such monitoring devices are not very easy toadjust, since in each instance both feeler levers must be regulatedseparately from one another with respect to a given yarn with regard tothe counter forces which act thereat.

SUMMARY OF THE INVENTION Hence, it will be recognized that thisparticular field of technology is still in need of apparatus formonitoring a thread or the like which is not associated with theaforementioned drawbacks and limitations of the prior art proposals.Therefore, it is a primary object of the present invention to provide animproved construction of monitoring device which effectively andreliably fulfills the existing need in the art.

Another and more specific object of the present invention aims at theprovision of a new and improved construction of thread monitor whichavoids the drawbacks of the heretofore known plucking or pick monitorsand additionally possesses a simpler construction and an improved modeof operation.

Yet a further significant object of the present invention relates to animproved construction of monitoring apparatus for threads or the likewhich is relatively simple in construction and design,- economical tomanufacture, extremely reliable in operation, not readily subject tobreakdown or malfunction, and requires a minimum of servicing andmaintenance.

A further objective of the invention is directed to replacing both ofthe mechanical-electrically operating feeler levers of the heretoforeknown plucking monitor by a single guide element for the thread and theelectrical contact by electronic means.

Now in order to implement these and still further objects of theinvention, which will become more readily apparent as the descriptionproceeds, the invention contemplates that the guide element is equippedwith a mechanical-electrical transducer possessing a contact body, thetransducer upon release of the thread from the contact body or uponstandstill of the thread generating an electrical signal serving totrigger a control operation or an indicating operation.

According to a first exemplary embodiment of the apparatus of thisdevelopment the guide element is constructed to possess a carrier orsupport arm which is pivotably mounted, this arm supporting at its freeend a tribe-electric transducer or piezoelectric transducer, by way ofexample. According to another manifestation of the invention the guideelement is fixedly mounted and constructed to be resilient, wherein thecontact body can be resiliently arranged relative to its support arm.

BRIEF DESCRIPTION OF THE DRAWING The invention will be better understoodand objects other than those set forth above, will become apparent whenconsideration is given to the following detailed description thereof.Such description makes reference to the annexed drawing in conjunctionwith which there will be described purely by way of example a threadmonitor of this development which is intended, for instance, to be usedat a circular knitting machine, and wherein:

FIG. 1 is a schematic side view of a thread monitor designed accordingto the teachings of the present invention;

FIG. 2 is a front view thereof;

FIG. 3 is a view of the thread monitor from the rear of FIG. 1 with thecover hood of the housing removed so as to expose internal structure;

FIG. 4 is an enlarged longitudinal sectional view through the outer endof the support arm of the thread monitor and which carries atribo-electric transducer;

FIG. 5 is a fragmentary sectional view of another embodiment of threadmonitor employing a piezoelectric transducer wherein the contact body isresiliently arranged relative to the fixedly mounted support or carrierarm; and

FIG. 6 is an end view of the variant embodiment of thread monitordepicted in FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Describing now thedrawing, according to the exemplary embodiment of thread monitordepicted in FIGS. I to 3 it will be recognized that the same comprises ametallic housing 1 which is of a size approximating that of a matchboxand consisting of a rectangular mounting plate 7 and a cover hood member8 and housing the remaining components.

There is further provided a guide element 2 which embodies a contactbody 3 and a carrier or support arm 4 formed of metal and in the form ofa right angle flexed small pipe. The one flexed leg 40 of the supportarm 4 is pivotably mounted by means of a bearing bushing or sleeve 5which is guided through the mounting plate 7. According to the showingof FIG. 4 at the outer end 4b of the support arm 4 there is mounted therotationally symmetrical contact body 3 formed of a hard insulatingmaterial, for instance oxide ceramic. The contact body 3 possesses acylindrical shaft 9 and a thickened or enlarged piston 10 whichfunctions as a stop for the thread F or the like and is provided at itsfront portion with a longitudinal or lengthwise bore 18 and at thepiston 10 with a counter-bore 19 of larger diameter which receives theend of the support arm 4. A conductor wire 16 (FIG. 3) is guided throughthe entire length of the support arm 4 and almost through the entirelength of the contact body 3. The front end or portion of this conductorwire 16 forms an electrode 20 which is fixed in bore 18 by means of anysuitable sealing compound 21 and is sealed towards the outside. Theelectrode 20 together with the contact body 3 and the sealing compoundor mass 21 forms a triboelectrical transducer which, when the thread For the like is traveling, delivers an electrical thread travel signal,and which electrical signal disappears upon rupture or standstill of thethread or when the thread slides off of the contact body 3.

According to the showing of FIG. 3 there is furthermore secured to themounting plate 7 an adjustable tensioning device encompassing thecomponents or parts 6, 13, 14, 15. The one end of a tension spring 14 ofthe tensioning device engages with a projection 11 which is fixedlyconnected with the inner end of the support arm 4 and bears under theaction of the force of spring 14 against a stop 12 which is secured tothe mounting plate 7. The other end of the tension spring 14 is attachedto the periphery of a disk 13 which can be adjusted in the peripheraldirection by means of an adjusting or adjustment knob 6 or the like, thedisk 13 being connected with the adjustment knob 6 by means of a shaft15.

Furthermore, at the inside of the mounting plate 7 there is mounted anelectronic unit 17 which serves to amplify and transform the threadtravel signal delivered by the tribe-electrical transducer. This threadtravel signal is delivered to the input of the electronic unit 17 bymeans of the conductor wire 16. An electrical cable 22 possessing anumber of conductors or lines 22' serves for the infeed of the supplyvoltage to the electronic unit or device 17 and for the delivery of theoutput signal.

With the benefit of the foregoing description of the embodiment ofthread monitor depicted in FIGS. 1 to 4 its mode of operation, whenemployed for instance at a not particularly illustrated circularknitting machine, will now be considered. As is well known in thecircular knitting art such type machine possesses, for instance, 24 or36 knitting stations or locations; each such knitting location hasassociated therewith a thread monitor which is mounted at a frame at aheight of at least one meter above the knitting location. The thread For the like travels from a supply spool, through a knot catcher, andfurther in the direction of the arrow a to the contact body 3, over andpast the latter downwardly in the direction of the arrow b, and finallyover a thread or yarn guide to the knitting location which directlyfollows the same. As illustrated in FIGS. I to 3 the guide element 2 isthus located in a slightly upwardly extending or slanted position, sothat the thread F will be held against the contact body 3 by the threadtension and the front end surface 10a of the piston 10 serves as a stopfor the thread. In any event with the aid of the adjustment knob 6 thetension of the spring 14 can be adjusted such that the guide element 2,during normal operation, retains the position which has been imparted toit, however is rocked downwardly as soon as the tension of the thread Fexceeds a predetermined value. As long as the thread F travels over thecontact body 3 then a thread travel signal is delivered to theelectronic unit or device 17 which indicates the proper functioning ofthe associated knitting location.

Now if by virtue of a blockage of or interference with the thread travelat the supply spool or the like or upon the arrival of a knot at theknot catcher the thread tension increases to an impermissibly highvalue, then the guide element 2 is rocked downwardly into a positionwhich has been indicated by the phantom or broken lines in FIG. 1, sothat the thread F slides off the contact body 3. Thereafter, the guideelement 2 is again returned upwardly into its original position by theforce of the spring 14. As soon as the thread is released from thecontact body 3 the thread travel signal is interrupted and due to theaction of the output signal generated by the electronic unit 17 upon asuitable shutdown or stop motion mechanism the knitting machine isshutdown or stopped. The time between sliding off of the thread untilshutting down the machine amounts to about 20 milliseconds. This time isso short that the length of the thread which is used until shutdown ofthe knitting location is smaller than the thread reserve which isprovided by the ejection of the thread from the thread monitor, so thatdepletion of such reserve and therefore thread rupture is positivelyprevented.

FIG. 5 illustrates a longitudinal sectional side view through the end ofa carrier or support arm 4' of an exemplary embodiment of thread monitorequipped with a piezoelectric transducer system which encompasses thecomponents 23 to 27, and FIG. 6 illustrates a view of the forward end ofthe guide element with the component or part 30 removed. A substantiallyU-shaped flexed holding or holder bracket 23 consisting of resilientmetal has a short leg 24 and a longer leg 25 which extends out of thetubular shaped support arm 4'. Between the legs 24 and 25 there isfixedly clamped internally of the support arm 4' a piezoelectric element26 in the form of a short cylinder by means of two insulating disks 27.The holding or holder bracket 23 is secured at the forward widened end40 of the support arm 4' by means of a small insulating tube 28 formedof soft elastic material. The inner compartment of the transducer system23-27 is sealed in a dustproof manner towards the outside by means of aclosure element 29 which likewise can consist of a soft elasticmaterial.

The protruding portion of the long leg 25, which possesses asubstantially rectangular cross-sectional configuration, carries' acontact body 3' which preferably consists of a hard ceramic material.This contact body 3 possesses an essentially semi-cylindrical shape andconsists of a shaft'9' and a piston 10'.

The piezoelectric element 26, as is known, is constructed as anelectrical polarized ceramic body or as a piezoelectric crystal with twoelectrodes (not particu larly shown) arranged at its opposite surfaces;the electrodes are connected by two conductor wires 16' with anelectronic unit 17, as the same has been depicted in FIG. 3.

As long as a thread F or the like is traveling with a normal tensionover the contact body 3' it bears against a stop or impact disk 30 andthe piezoelectric element 26 delivers an electrical thread travelsignal. lf, however, the thread tension increases to an impermissiblyhigh value, then, the contact body 3', owing to the spring or resilientaction of the bracket 23 and the soft elastic tube 28, is rockeddownwardly relative to the support arm 4, so that the thread F slidesoff the contact body 3. In this case the carrier or support arm 4 ispreferably attached so as to be non-movable at the mounting plate 7 andthe provision of a tensioning device in the housing is not necessary.

For adjusting the response threshold of the thread monitor, i.e. theforce which is necessary for throwingoff or rejecting the thread F,different measures can be provided for such thread monitor. Thus, thecontact body 3' can be equipped with a stop which is adjustable in itslengthwise direction and which is in the form of a disk 30 as such hasbeen shown in FIG. 5. During normal operation the thread F or the likebears against this disk-stop 30. By adjusting the disk 30 the effectivelever arm and thus the moment, with which the force exerted by thetravel of the thread F acts upon the long arm of the bracket 23 and andits mounting, is changed. A further possibility for changing theresponse threshold resides in altering the inclination of the contactbody 3 towards the horizontal or towards the direction of travel of thethread in that the support or carrier arm 4' is adjustably mounted asconcerns its angular position relative to the housing, or however theentire thread monitor can be adjustably mounted at its support by meansof a rotary bearing.

The described thread monitors are not only of simpler construction thanthe known plucking or pick monitors, since they only possess a singlepivotable element, but they are also insensitive against dustcontamination of the guide element and the contact body; additionallythey do not possess any electrical contacts which are to be mechanicallyactuated and which are susceptible to dust contamination and corrosion,and furthermore they respond decisively quicker than the known pluckingmonitors, so that there can be positively prevented consumption of thethread reserve with subsequent thread rupture and the thus brought aboutejection of the material hose from the machine. Also in the case ofthread rupture without actuating the guide element there nonethelessoccurs standstill of the machine owing to the disappearance of thethread travel signal.

Finally it is still to be remarked that tribe-electrical thread or yarnmonitors of different type are known and in principle have already beendisclosed in Swiss Pat. No. 479,478, the disclosure of which isincorporated herein by reference. Also piezoelectrical thread monitorsare known to the art, for instance as disclosed in Swiss Pat. No.439,791, the disclosure of which is likewise incorporated herein byreference.

While there is shown and described present preferred embodiments of theinvention, it is to be distinctly understood that the invention is notlimited thereto, but may be otherwise variously embodied and practicedwithin the scope of the following claims. Accordingly,

What is claimed is:

1. An apparatus for monitoring the travel and tension of a thread or thelike preferably at a textile machine, comprising a guide element, meansfor holding the guide element by means of a counter force against atension force normally exerted by the thread in a position in which thethread is in contact with the guide element, but in the presence of animpermissibly high tension force prevailing at the thread said guideelement releases the thread, said guide element being equipped with atribe-electric transducer, said tribo-electric transducer embodying asubstantially elongate contact body equipped with a lengthwise bore andan electrode arranged in said lengthwise bore, said tribe-electrictransducer upon release of the thread from the contact body or uponstandstill of the thread generating an electrical signal serving totrigger a predetermined operation.

2. The apparatus as defined in claim 1, wherein said predeterminedoperation is a control operation.

3. The apparatus as defined in claim 1, wherein said predeterminedoperation is an indicating operation.

4. The apparatus as defined in claim 1, further including a stationarycomponent, said guide element comprising a support arm, means forpivotably mounting the support arm at the stationary component, and saidholding means incorporating a spring for retaining the support arm in awork position.

5. The apparatus as defined in claim 1, further including a housinghaving a component, and means for mounting the guide element at saidhousing component, said transducer having at least one electrode, anelectronic unit housed at said housing and connected with said at leastone electrode of the transducer.

6. The apparatus as defined in claim 5, wherein said housing is providedwith an adjustable tensioning device.

7. An apparatus for monitoring the travel and tension of a thread or thelike preferably at a textile machine, comprising a guide element, meansfor holding the guide element by means of a counter force against atension force normally exerted by the thread in a position in which thethread is in contact with the guide element, but in the presence of animpermissibly high tension force prevailing at the thread said guideelement releases the thread, said guide element being equipped with apiezoelectric transducer possessing a contact body, a substantiallyU-shaped flexed holding bracket formed of resilient material, saidholding bracket having a pair of legs, said piezoelectric transducerfurther including a piezoelectric element arranged between the legs ofsaid holding bracket, said piezoelectric transducer upon release of thethread from the contact body or upon standstill of the thread generatingan electrical signal serving to trigger a predetermined operation.

8. The apparatus as defined in claim 7, further including a stationarycomponent, said guide element including means imparting thereto aresilient construction, and means for fixedly mounting said guideelement at the stationary component.

9. The apparatus as defined in claim 7, said guide element including asupport arm, and means for resiliently arranging the contact bodyrelative to the support arm. =l 1

1. An apparatus for monitoring the travel and tension of a thread or thelike preferably at a textile machine, comprising a guide element, meansfor holding the guide element by means of a counter force against atension force normally exerted by the thread in a position in which thethread is in contact with the guide element, but in the presence of animpermissibly high tension force prevailing at the thread said guideelement releases the thread, said guide element being equipped with atribo-electric transducer, said tribo-electric transducer embodying asubstantially elongate contact body equipped with a lengthwise bore andan electrode arranged in said lengthwise bore, said tribo-electrictransducer upon release of the thread from the contact body or uponstandstill of the thread generating an electrical signal serving totrigger a predetermined operation.
 2. The apparatus as defined in claim1, wherein said predetermined operation is a control operation.
 3. Theapparatus as defined in claim 1, wherein said predetermined operation isan indicating operation.
 4. The apparatus as defined in claim 1, furtherincluding a stationary component, said guide element comprising asupport arm, means for pivotably mounting the support arm at thestationary component, and said holding means incorporating a spring forretaining the support arm in a work position.
 5. The apparatus asdefined in claim 1, further including a housing having a component, andmeans for mounting the guide element at said housing component, saidtransducer having at least one electrode, an electronic unit housed atsaid housing and connected with said at least one electrode of thetransducer.
 6. The apparatus as defined in claim 5, wherein said housingis provided with an adjustable tensioning device.
 7. An apparatus formonitoring the travel and tension of a thread or the like preferably ata textile machine, comprising a guide element, means for holding theguide element by means of a counter force against a tension forcenormally exerted by the thread in a position in which the thread is incontact with the guide element, but in the presence of an impermissiblyhigh tension force prevailing at the thread said guide element releasesthe thread, said guide element being equipped with a piezoelectrictransducer possessing a contact body, a substantially U-shaped flexedholding bracket formed of resilient material, said holding brackethaving a pair of legs, said piezoelectric transducer further including apiezoelectric element arranged between the legs of said holding bracket,said piezoelectric transducer upon release of the thread from thecontact body or upon standstill of the thread generating an electricalsignal serving to trigger a predetermined operation.
 8. The apparatus asdefined in claim 7, further including a stationary component, said guideelement including means imparting thereto a resilient construction, andmeans for fixedly mounting said guide element at the stationarycomponent.
 9. The apparatus as defined in claim 7, said guide elementincluding a support arm, and means for resiliently arranging the contactbody relative to the support arm.